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| United States Patent |
5,250,086
|
|
McEachron
, et al.
|
October 5, 1993
|
Multi-layer metal coated diamond abrasives for sintered metal bonded
tools
Abstract
Multi-layer coated diamond abrasive particles which exhibit good retention
in abrasive tools and are simpler to manufacture are provided, wherein the
coating comprises a single homogenous, carbide forming metal primary
layer, preferably of chromium, and at least one non-carbide forming
secondary layer, preferably of nickel, iron, cobalt, or alloys thereof.
The primary layer is preferably applied so as to chemically bond to the
surface of the diamond abrasive particles without sintering following
deposition by using chemical vapor deposition or packed salt bath
deposition.
| Inventors:
|
McEachron; Roger (Worthington, OH);
Connors; Edward J. (Westerville, OH);
Slutz; David E. (Columbus, OH)
|
| Assignee:
|
General Electric Company (Worthington, OH)
|
| Appl. No.:
|
857132 |
| Filed:
|
March 25, 1992 |
| Current U.S. Class: |
51/309; 51/293; 51/295 |
| Intern'l Class: |
B24D 003/02 |
| Field of Search: |
51/293,295,309
|
References Cited
U.S. Patent Documents
| 2746888 | May., 1956 | Ross | 117/221.
|
| 3465416 | Sep., 1969 | Wellborn et al. | 29/473.
|
| 3556839 | Oct., 1967 | Roy | 117/100.
|
| 3924031 | Dec., 1975 | Nicholas et al. | 51/295.
|
| 4063907 | Dec., 1977 | Lee et al. | 51/295.
|
| 4289503 | Sep., 1981 | Carrigan | 51/309.
|
| 4378975 | Apr., 1983 | Tomlinson et al. | 51/309.
|
| 5024680 | Jun., 1991 | Chen et al. | 51/295.
|
| Foreign Patent Documents |
| 0004177 | Sep., 1978 | EP.
| |
Primary Examiner: Bell; Mark L.
Assistant Examiner: Thompson; Willie J.
Claims
What is claimed is:
1. An abrasive particle suitable for use in a sintered metal bonded
abrasive tool comprising a diamond abrasive having a multi-layer coating
consisting essentially of one homogeneous carbide forming metal primary
layer deposited by chemical vapor deposition, or packed salt deposition
and a non-carbide forming metal secondary layer deposited by electroless
or electrolytic deposition.
2. An abrasive particle as in claim 1, wherein said non-carbide forming
metal secondary layer comprises cobalt, iron, nickel, or alloys thereof.
3. An abrasive particle as in claim 2, wherein the amount of said
non-carbide forming metal secondary layer ranges from 10 to 50 wt %, based
on the weight of the uncoated diamond abrasive particle.
4. An abrasive particle as in claim 3, wherein the non-carbide forming
metal secondary layer is comprised of one layer of nickel/phosphorus,
nickel, cobalt, or cobalt/phosphorus.
5. An abrasive particle as in claim 2, having two different non-carbide
forming metal secondary layers.
6. An abrasive particle as in claim 6, wherein the diamond abrasive
particles have an average particle size in the range of 1 to 1500 .mu.m.
7. An abrasive particle as in claim 1, wherein the carbide forming metal
primary layer has a thickness ranging from 0.1-10 .mu.m.
8. An abrasive particle suitable for use in sintered metal bonded abrasive
tools comprising a diamond abrasive having a multi-layer coating
consisting essentially of one homogeneous chromium metal primary layer
chemically bonded to the surface of the diamond abrasive and at least one
non-carbide forming metal secondary layer.
9. An abrasive particle as in claim 8, wherein said non-carbide forming
metal secondary comprises cobalt, iron, nickel, or alloys thereof.
10. An abrasive particle as in claim 8, wherein the amount of said
non-carbide forming secondary layer ranges from 10 to 50 wt %, based on
the weight of the uncoated diamond abrasive particle.
11. An abrasive particle as in claim 10, wherein the non-carbide forming
metal secondary layer is comprised of one layer of nickel/phosphorus,
nickel, cobalt, or cobalt/phosphorus.
12. An abrasive particle as in claim 9, having two different non-carbide
forming secondary layers.
13. An abrasive particle as in claim 8, wherein the diamond abrasive
particles have an verage particle size in the range of 1 to 1500 .mu.m.
14. An abrasive particle suitable for use in a sintered metal bonded
abrasive tool comprising a diamond abrasive having a multi-layer coating
consisting essentially of one homogeneous chromium metal primary layer
deposited by chemical vapor deposition, or packed salt deposition and a
non-carbide forming metal secondary layer deposited by electroless or
electrolytic deposition.
15. An abrasive particle as in claim 14, wherein said non-carbide forming
metal secondary layer comprises cobalt, iron, nickel, or alloys thereof.
16. An abrasive particle as in claim 14, wherein the chromium metal primary
layer has a thickness ranging from 0.1-10 .mu.m.
17. A process for the preparation of coated diamond abrasive particles for
use in sintered metal bonded abrasive tools, said process comprising
applying one homogeneous carbide forming metal primary layer to the
surface of said diamond abrasive particles by chemical vapor deposition or
packed salt deposition and applying at least one secondary layer of a
non-carbide forming metal by electrolytic deposition, electroless
deposition, or chemical vapor deposition.
18. A process according to claim 17, wherein the homogenous carbide forming
met primary layer consists essentially of chromium and is chemically
bonded to the diamond abrasive particle without a separate sintering step.
19. A process according to claim 17, wherein the secondary layer of
non-carbide forming metal is applied by electroless deposition or
electrolytic deposition.
20. A process according to claim 17, wherein the carbide forming metal
primary layer is applied at a thickness ranging from 0.1 to 10 .mu.m, and
the secondary layer is applied in an amount in the range of 10-50 wt %,
based on the weight of the uncoated diamond abrasive particles.
21. A process according to claim 20, wherein two different secondary layers
are applied.
22. A method according to claim 11, wherein the secondary layer comprises
nickel iron, cobalt, or an alloy thereof.
23. A process according to claim 17, comprising the additional steps of
mixing the coated diamond abrasive particles with a sinterable metal,
pressing the mixture at ambient temperature to form a solid mass of a
desired shape and heating the solid mass to a temperature sufficiently
high to sinter said sinterable metal.
24. A sintered metal bonded abrasive tool comprising a sintered metal
matrix and abrasive particles of claim 1.
Description
BACKGROUND OF THE INVENTION
This invention relates to diamond abrasive particles having a multi-layer
metal coating and processes for producing the same. These coated diamond
abrasives find particular use in sintered metal bonded tools where the
multi-layer coating aids retention of the diamond abrasives within such
tools and also aids tool wear resistance.
It is well known in the art that metal coatings can improve the retention
of diamond abrasive particles in the matrices of abrasive tools such as
those used to saw stone and concrete. Metal coated diamond abrasives are
commercially available with nickel coatings typically applied by
electroless deposition. While such abrasives provide good performance,
improvements are desired to reduce the premature loss of diamond abrasive
particles and reduce the wear of abrasive tools.
Nickel coatings applied by electroless deposition are not chemically bound
to the diamond surface. Metals which adhere to diamond surfaces more
strongly are well known and include molybdenum, titanium and chromium,
which are carbide formers and are typically chemically vapor-deposited or
sputtered onto diamond surfaces. Examples of such coatings and processes
for depositing them are disclosed in U.S. Pat. No. 3,465,916;
EP-A-79/300,337.7; U.S. Reissue No. 34,133; and U.S. Pat. No. 4,063,907.
Although these coatings bond more strongly to diamond surfaces than nickel
coatings, these coatings are usually oxidized and can be brittle,
depending on the carbide formed.
Carbide forming metal layers have been used as part of multi-layer coatings
on diamond particles to aid retention within a tool matrix. U.S. Pat. No.
3,924,031 discloses a multi-layer coating for diamond particles wherein
the first layer comprises an alloy with a base metal of copper, nickel or
iron and a carbide-forming metal such as titanium, chromium or vanadium.
This alloy layer may be over coated with another layer such as nickel by
electroless or electrolytic deposition. The alloys comprise at most 30 wt.
% of the carbide forming metal and, to form the carbide, the coating is
heated at high temperatures after deposition by vacuum evaporation or
sputtering.
U.S. Pat. No. 4,378,975 describes the use of chromium as a first coating on
pelletized diamond particles which are in turn used to form abrasive
bodies. A sintered copper/nickel alloy forms the outer wear-resistant
coating on these pelletized particles. It is unknown whether the chromium
layer forms a carbide, although the green pellets are sintered at
temperatures of 900.degree. C. in forming the pelletized particles.
U.S. Pat. No. 5,024,680 describes the use of a chromium, titanium or
zirconium carbide-forming layer as part of a multi-layer coating on
diamond particles to aid retention within a matrix. Two carbide-forming
layers are applied; one thin base layer and a thick oxidation-resistant
secondary layer. A third non-carbide-forming layer applied by electroless
techniques is optional. The base carbide layer of chromium, zirconium or
titanium is applied by metal vapor deposition, preferably followed by
heating of the coated particle to form the carbide. Chemical vapor
deposition of this layer is said to provide no advantage. The secondary
carbide-forming metal layer of tungsten or tantalum can be applied by CVD
followed by heating of the layer to provide adequate carburization.
These procedures for applying multi-layer coatings are complex in that
either metal alloys are applied as one of the layers, or three distinct
layers are used. In addition, these procedures provide increased bonding
strength between the diamond particles and the tool matrix through
carburization of the metal coating, during which the diamond particles are
exposed to high temperatures. High temperatures can cause degradation of
the diamond crystal, which is detrimental to the performance of the
cutting tool. Chen et al. (U.S. Pat. No. 5,024,680) recognizes this
problem but provides no solution other than to avoid excess carburization.
It is desirable to apply multi-layer coatings to diamond by a simpler
method which will aid its retention within the matrix of an abrasive tool
without degrading the diamond particle and improve tool wear resistance.
It is also desirable to provide multi-layer coatings to diamond which will
enhance the wear performance of an abrasive tool.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide metal
coated diamond abrasive particles with improved retention and wear
performance within sintered metal bonded abrasive tools comprising only
two metal layers.
Another object of this invention is to provide a process for making metal
coated diamond abrasive particles having a strongly adherent, multi-layer
metal coating that aids particle retention and wear performance within
abrasive tools while limiting the exposure of these particles to thermal
cycles which cause their degradation.
It is a further object of the present invention to provide abrasive tools
which comprise multi-layer metal coated diamond abrasive particles having
a strongly bonded chromium base layer and a compatible secondary layer.
Upon further study of the specification and appended claims, further
objects and advantages of this invention will become apparent to those
skilled in the art.
These and other objects are achieved by a process wherein diamond abrasive
particles are coated with at least two metal layers. A carbide-forming
layer provides the primary layer and is chemically bonded to the surfaces
of the diamond abrasive particles. These carbide-forming layers are
comprised of tungsten, titanium, tantalum, zirconium, molybdenum, hafnium,
chromium, vanadium, silicon, niobium, or a carbide, boride, or nitride
thereof. The outer metal layer comprises nickel, cobalt, iron, or alloys
thereof, preferably applied by electrolytic deposition, electroless
deposition, or CVD techniques and most preferably by electroless
deposition. The secondary coating typically ranges from 10-50 wt %,
preferably 20-35 wt %, of the uncoated diamond abrasive particles. The
abrasive tools provided by this invention comprise multi-layer metal
coated diamond abrasive particles bonded within a sintered metal matrix.
Conventional methods for bonding the coated particles within a matrix to
form tools can be utilized.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Diamond abrasive particles utilized in this invention are of the size
conventionally used in sintered metal bonded tools such as, for example,
those of 20/80 U.S. mesh size. The size of the particles can vary widely
within the range of 1/1500 .mu.m, preferably 150-1000 .mu.m, and most
preferably 200-600 .mu.m. Conventionally sized diamond abrasive particles
are sufficiently large so as to provide a cutting profile for the tools
desired and not be excessively diluted by the metal coatings to be
applied.
The diamond abrasive particles used in this invention can be natural or
synthetic but are typically obtained by conversion of graphite under high
pressure and high temperature (HP/HT), either with or without a catalyst.
Preferably, the diamonds are of a size within the range of from 20 to 80
U.S. mesh and are obtained directly from a conversion process. However,
the diamond particles utilized can be obtained from larger sized materials
which are milled or pulverized by conventional techniques.
The diamond abrasive particles are initially coated with a carbide-forming
metal such as silicon, chromium, titanium, tungsten, zirconium, hafnium,
vanadium, niobium, tantalum, molybdenum, or a carbide, boride, or nitride
thereof. Chromium is preferred. A suitable method for depositing some of
these metals, such as chromium, is a packed salt cementation process
operating between about 600-1000.degree. C. for chromium, preferably
between 800-950.degree. C. Abrasive diamond particles are typically
immersed within a molten bath of one or more alkali or alkaline earth
halides with the carbide- forming metal. This technique allows for
chemical bonding of the carbide-forming metal to the diamond particle
surface on formation of metal carbide. The details of a suitable salt bath
deposition process can be found in U.S. Pat. No. 2,746,888. The
carbide-forming layer can be applied in a wide range of thicknesses.
Chromium is preferably at a thickness ranging from 0.1 to 10 .mu.m, more
preferably 2-5 .mu.m.
Other methods for applying the primary carbide-forming layer are also
suitable if significant chemical bonding is obtained with limited exposure
to harmful thermal cycles. Chemical vapor deposition (CVD) techniques are
most preferred and, more preferably, low pressure chemical vapor
deposition (LPCVD) techniques are used. LPCVD techniques are well known in
the art. These techniques utilize reactive gas mixtures at sub-atmospheric
conditions and high substrate temperatures to deposit carbide-forming
metals, such as chromium. Prior to coating the diamond abrasive particles,
it is preferable to remove oxides and volatile impurities from the
surface, particularly surface oxide contaminants. A suitable technique for
removing these impurities and depositing metal layers by LPCVD is
described in U.S. Pat. No. 4,289,503, which is directed to removing oxides
on cubic-boron nitride.
The secondary layer can be deposited by a number of techniques which
include electroless deposition, electrolytic deposition, and vapor
deposition techniques. Preferably, these secondary layers are thicker than
the primary layer and provide a rough surface. If desired, the secondary
layer may be applied by LPCVD or salt bath deposition techniques.
Non-carbide forming metals are preferred for use as the secondary layer.
They include nickel, cobalt and iron. Of these metals, nickel is the most
preferred and is preferably deposited by electroless coating techniques
with a nickel/hypophosphite solution which deposits a small percentage of
phosphorus (6-11 wt. %). A suitable electroless deposition process is
described in U.S. Pat. No. 3,556,839.
While the coated abrasive particles of the present invention typically
comprise only one primary carbide-forming layer and one
non-carbide-forming secondary layer, additional layers of
non-carbide-forming metals are optional. For example, thin
nickel/phosphorus layers applied by electroless deposition techniques
between the chromium layer and outer coatings of cobalt or iron can be
used.
The secondary metal coating is preferably applied at a level of about 10-50
wt. % of the abrasive particles. Most preferably, the coating is applied
in an amount of between 20-35 wt. % of the abrasive particles. The primary
coating is relatively thin; so the total coating applied may range from
above 10 wt % to about 60 wt % of the diamond abrasive. Preferred levels
for the total coating fall within the range of 20-40 wt. % of the uncoated
particles. The thickness of the metal coating may be varied to control
properties of tools such as particle retention, lubrication and heat
diffusion characteristics. One of ordinary skill in the art can vary the
coating thicknesses and diamond granule sizes for the tool intended by
routine investigation. After the diamond abrasive particles are coated
with multiple metal layers, they are used to form an abrasive tool bonded
by a sintered metal.
The coated diamond abrasive particles are impregnated within a suitable
metal matrix by conventional techniques when used in abrasive tools. For
example, a mixture of the coated abrasives and metal particles can be
pressed at ambient temperature to the shape desired and the pressed
article heated so as to sinter the metal therein. Suitable metals include
nickel, cobalt, etc. Preferred components are tool inserts for saw blades
of 30-40 mesh size diamond particles coated with chromium and nickel and
bound by a sintered nickel, cobalt, and/or cobalt/bronze matrix. These
tool inserts can be of any form or shape, particularly those shapes which
are conventional for tools used to cut stone and concrete.
Without further elaboration, it is believed that one skilled in the art
can, using the preceding description, utilize the present invention to its
fullest extent. The following preferred specific embodiments are,
therefore, to be construed as merely illustrative, and not limitative of
the remainder of the disclosure in any way whatsoever.
In the foregoing and in the following examples, all temperatures are set
forth in degrees Celsius and unless otherwise indicated, all parts and
percentages are by weight.
The entire disclosure of all applications, patents and publications, cited
above and below, are hereby incorporated by reference.
EXAMPLES
Chromium-Coated Diamond Abrasives
Synthetic diamond abrasive particles under the trade designations MBS-70,
MBS-750, and MBS-760, all of 30/40 mesh size, provided by the General
Electric Company, are each separately coated with chromium in a salt bath.
The salt bath comprises chromium metal and a mixture of salts including
sodium chloride, potassium chloride, and calcium chloride. The temperature
of the bath is maintained at between 850-900.degree. C. After about two
hours of treatment, the particles have a chromium coating of from 0.5-1.0
.mu.m in thickness.
Titanium-Coated Diamond Abrasives
Synthetic diamond abrasive particles under the trade designations MBS-70,
MBS-750, and MBS-760, all of 30/40 mesh size, provided by the General
Electric Company, are each separately coated with titanium in a salt bath.
The salt bath comprises titanium metal, NaCl, KCl, and CaCl.sub.2. The
temperature of the bath is between 850-900.degree. C. After about two
hours, the particles have a titanium layer of about 0.25-1.0 .mu.m in
thickness.
Secondary Coating: Electroless Deposition
Chromium-coated MBS-750 diamond abrasive particles and titanium-coated
MBS-750 diamond abrasive particles, as described above, are separately
over coated with a cobalt/phosphorus layer by an electroless deposition
process consistent with the procedures described in U.S. Pat. No.
3,556,839. Chromium-coated MBS-760 and titanium-coated MBS-760 are
separately over coated with a nickel/phosphorus layer. A hypophosphite
solution of cobalt or nickel is used as the plating solution. The pH is
between 4-5.5 for the nickel solution and 12-14 for the cobalt solution.
The process temperature maintained at between 60.degree.-95.degree. C. The
metal layers are individually deposited from a series of separate baths.
When the nickel or cobalt is depleted, the bath is discarded, and a fresh
bath is used until the desired coating weight is obtained. Typically, from
5-20 baths are used, depending on the size of the bath container, the size
of the abrasive particles, and the initial concentration of the bath. The
nickel/phosphorus layers and the cobalt/phosphorus layers are deposited in
an amount of from 20-40 wt %, based on the original weight of the abrasive
particles, and have a phosphorus content of from 6-11 wt %.
Secondary Coating: Electrolytic Deposition
Portions of the titanium-coated and chromium-coated MBS-70, MBS-750, and
MBS-760 diamond abrasives described above are separately over coated with
either a nickel or cobalt layer by a conventional electrolytic deposition
technique. The amount of nickel or cobalt applied ranges from 20-40 wt %,
based on the original weight of the abrasive particles.
Particle Retention
Uncoated and coated diamond abrasive particles (MBS-70, MBS-750, and
MBS760), as described above, are separately bound within test bars using a
conventional cobalt matrix for stone-cutting abrasive tools.
The test bars are obtained by mixing the abrasive particles described above
with the matrix alloy in powder form in a ratio conventionally used for
abrasive tools. The mixture is compressed into the shape of a test bar,
sintered at conventional temperatures used for the matrix alloy, and
cooled to ambient temperature. The test bars are 2"long, 1/4" wide, and
1/4" in height.
The relative diamond retention in the bars produced is tested by breaking
the bar across its width in an Instrom machine, which applies a constant
force (about 2.0.times.10.sup.4 m/min.). The percent retention reported in
Tables I-III below is equivalent to the percentage of broken diamond
crystals across the break of the test bar.
TABLE I
______________________________________
Abrasive particle MBS-70
Retention
______________________________________
Uncoated 10%
Cr 20%
Cr/Co 33%
Cr/Ni 44%
Ti 6%
Ti/Ni 52%
______________________________________
TABLE II
______________________________________
Abrasive Particle MBS-750
Retention
______________________________________
Uncoated 4%
Cr 17%
Cr/Ni 55%
Cr/Co 56%
Cr/Co--P (electroless)
32%
Ti 8%
Ti/Ni 26%
Ti/Co--P (electroless)
22%
______________________________________
TABLE III
______________________________________
Abrasive Particle MBS-760
Retention
______________________________________
Uncoated 2%
Cr 28%
Cr/Ni 47%
Cr/Co 58%
Cr/Ni--P (electroless)
62%
Ti 5%
Ti/Ni 42%
Ti/Ni--P (electroless)
5%
______________________________________
These results are approximate but show that the coated diamond particles of
the invention are significantly superior in retention to uncoated diamond
abrasive particles and diamond particles coated with only one layer
(chromium or titanium). In addition, this data shows that particles with a
multi-layer coating having a primary layer of chromium are consistently
superior in retention to particles with a titanium primary layer.
Wear Performance
Synthetic diamond abrasive particles under the trade designations MBS-750
and MBS-760, both of 30/40 mesh size, provided by the General Electric
Company, are each coated by the procedures described above in five
variations. These include a mono-layer of carbide-forming chromium, a dual
layer of carbide-forming chromium, and either an electroless nickel or
cobalt layer and a dual layer of carbide-forming chromium and either an
electroplated cobalt or nickel layer. The composition and quantity (wt %)
o metal coating on the different particles, numbered 1-10, are shown
below. The total weight percentages of the combined metal layer coatings
on the then different coated particles are as follows:
______________________________________
MBS-750/Particle No.
Cr-inner 6.03/1
Cr/Co electroplate
27.1/2
Cr/Co--P electroless
23.95/3
Cr/Ni electroplate
27.13/4
Cr/Ni--P electroless
25.33/5
MBS-760/Particle No.
Cr-inner 4.07/6
Cr/Co electroplate
24.6/7
Cr/Co--P electroless
27.89/8
Cr/Ni electroplate
24.62/9
Cr/Ni--P electroless
24.8/10
______________________________________
The metal-coated diamond particles are processed into segments for 7"
diameter saw blades. The bond matrix is 100% cobalt, hot-processed under
5000 psi at 850.degree. for three minutes. A total of nine arc segments
(0.240".times.0.140".times.0.20") are induction-brazed onto a circular
steel core to produce 7" nominal diameter blades for testing wear
performance.
Prior to testing, each saw blade is conditioned by trueing with a silicon
carbide wheel, lightly dressing the blade open by sawing a sandstone block
and sawing Barre granite under testing conditions to develop a stabilized
cutting surface. The blade is then measured at three pre-selected
locations long each segment's length (leading edge, center, and trailing
edge), and an average of the radial height is calculated for each saw
blade. The radial measurements are made to the nearest 0.0001".
The saw tests are conducted on a modified surface grinder sawing Barre
granite at the rate of 46.5 in.sup.2 /min (300 cm.sup.2 /min). The sawing
is carried out under alternating upcut and downcut sawing at a 0.344"
(10.0 mm) depth of cut and a traverse rate of 118.1 in/min (3 m/min). The
rotational speed of the blade during all tests was fixed at 5904 SFPM (30
m/sec). Water coolant is applied to the blade during sawing at a delivery
rate of 3.5 gal/min (38 l/min).
The results of the 7" blade tests are expressed in a wear performance
number. This number is calculated by dividing the amount of granite sawed
(square inches) by the average blade radial wear in 0.001 inches. Under
normal circumstances, the amount of granite sawed by the blades of any
particular test series is determined as the minimal amount necessary to
generate at least 0.010 inches of radial blade wear. The specific wear
performance results are shown in Tables IV-VII.
TABLE IV
______________________________________
Wear Performance of MBS-750 Diamond
Coated With Chromium/Cobalt
Average
Particle No.
Coating Tests 1 and 2Wear Life
______________________________________
Control Control
None None
##STR1##
2 2 Cr/Co Cr/Co
##STR2##
3 3 Cr/CoP Cr/CoP
##STR3##
______________________________________
TABLE V
______________________________________
Wear Performance of MBS-750 Diamond
Coated with Chromium and Chromium/Nickel
Average
Particle No.
Coating Tests 1 and 2Wear Life
______________________________________
Control Control
None None
##STR4##
1 1 Cr Cr
##STR5##
4 4 Cr/Ni Cr/Ni
##STR6##
5 5 Cr/NiP Cr/NiP
##STR7##
______________________________________
TABLE VI
______________________________________
Wear Performance of MBS-760 Diamond
Coated with Chromium and CHromium/Cobalt
Average
Particle No.
Coating Tests 1 and 2Wear Life
______________________________________
Control Control
None None
##STR8##
6 6 Cr Cr
##STR9##
7 7 Cr/Co Cr/Co
##STR10##
8 8 Cr/CoP Cr/CoP
##STR11##
______________________________________
TABLE VII
______________________________________
Wear Performance of MBS-760 Diamond
Coated with Chromium and Chromium/Nickel
Average
Particle No.
Coating Tests 1 and 2Wear Life
______________________________________
Control Control
None None
##STR12##
6 6 Cr Cr
##STR13##
9 9 Cr/Ni Cr/Ni
##STR14##
10 10 Cr/NiP Cr/NiP
##STR15##
______________________________________
The above data shows that particles with multi-layer coatings having an
outer secondary metal coating deposited electrolessly provide superior
wear performance over particles with secondary metal coatings deposited
electrolytically and also uncoated particles. Some of the multi-layer
coatings with a secondary layer of electrolytically deposited cobalt
provide superior wear performance over similar particles with only a
chromium mono-layer.
The preceding examples can be repeated with similar success by substituting
the generically or specifically described reactants and/or operating
conditions of this invention for those used in the preceding examples.
From the foregoing description, one skilled in the art can easily
ascertain the essential characteristics of this invention, and without
departing from the spirit and scope thereof, can make various changes and
modifications of the invention to adapt it to various usages and
conditions.
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